Gear bearing systems combine the functions of gears and bearings to allow compact gear sets that provide both functions. Gear bearings may be joined together in a variety of applications, such as in planetary gear bearing systems. In planetary gear bearing systems, gear bearings are arranged to effect drive speed reductions. In such systems, drive speed reduction may be achieved through the use of phase-shifted gear bearings, which are gear bearings coupled together where the gear teeth of one bearing are offset relative to the gear teeth from the other bearing.
There are at least three problems with phase-shifted gear bearings: First, gear teeth must be of a particular configuration to allow meshing. For example, gear teeth on a gear bearing may need to be beveled at the point where they intersect with the gear teeth on another gear bearing such that they mesh properly. Additionally, the gear teeth must be numerically configured with integer ratios in order for proper meshing to occur. That is, the teeth of one gear bearing must be of a uniform ratio to the teeth of the other gear bearing (13:15, 15:16, 33:34, etc.). Finally, since the gear teeth of one gear bearing must exactly intermesh with the gear teeth of another gear bearing in order for a phased gear bearing to operate properly, such systems are susceptible to failure due to improper machining tolerances.
Attempts to increase the packaging density of conventional gear systems have been generally limited to cascaded gear reduction designs or ball screw and linkage designs. These systems may be difficult and/or costly to implement due to issues such as the high degree of precision required in machining and fitting. A conventional phase-shifted gear bearing system reduces the complexity and number of parts, but may place even higher demands on precision.